This application claims the benefit of European Application No. 00402203.4, filed Aug. 2, 2000.
1. Field of the Invention
The present invention relates generally to a switching device for an optical communication system. More particularly, the present invention is directed to a thermo-optical switch which can be integrated into a semi-conductor substrate.
2. Technical Background
As optical communication systems evolve, there is a growing demand for optical switching devices. Integrated optical switching devices are optical components commonly used for building optical communication networks. In order to realize an integrated optical switching device, several scientific principles and mechanisms may be used. One such principle is the thermo-optic effect. When this principle is applied to silica waveguides, the design of the device is usually based on a Mach-Zehnder interferometer. The power response of the device is obtained by creating a path difference between the two optical waveguides of the interferometer. This path difference is obtained by controlling the temperature difference between the two waveguides by way of metallic heaters. Thus, the switch speed of the device depends on the kinetics of the thermal variation between the two waveguides.
Integrated optical switch devices are currently manufactured on a silicon substrate, instead of silica, in order to obtain a high switch speed due to the better diffusion of the heat in the silicon. One or more silica glass waveguides are then formed on a surface of the silicon substrate. The silica glass waveguide and the silicon substrate have different coefficient of thermal expansion (CTE). This leads to stresses within the device including polarization dependence. Moreover, it creates a warpage of the silicon wafer, generating concerns in both the photolithographic and the pigtailing processes.
Accordingly, it is desirable to provide a technique for manufacturing integrated optical switch devices having a higher switching speed by building these switching devices on a silica substrate. It is also desirable to provide an optical switch having integrated features which overcome the problems with optical switches manufactured on other types of substrates.
In accordance with the teachings of the present invention, an optical switch is disclosed. The optical switch includes a substrate having a first surface and a second surface. At least one optical waveguide is formed below the first surface of the substrate. A heating element is disposed on the first surface of the substrate. The heating element is also disposed in proximity to the at least one optical waveguide. A cavity is formed in the second surface of the substrate. The cavity is also disposed in proximity to the at least one optical waveguide. A heat conductive material is disposed within the cavity.
It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate various features and embodiments of the invention, and together with the description serve to explain the principles and operation of the invention.